Cross-wound bobbins, also called cheeses or cheese packages, are supply bobbins from which a yarn is unwound and delivered to a yarn-using machine, such as a weaving machine or knitting machine. The cheese cone of the cross-wound bobbin is self-supporting and does not require end plates on the face ends. The hold within the cheese cone is achieved because the yarn or thread is wound up helically at a relatively high pitch traverse, rather than with windings close together as in a flanged bobbin with walls on the ends. The pitch traverse of the helical lines is high in order that the yarn in the individual layers of yarn will intersect multiple times, thus stabilizing the layer of yarn beneath it. At the same time, it forms an enveloping surface for the layer underneath.
The angle of inclination or crossing angle at which the yarns in the individual layers intersect prevents the yarns from forcing their way in between individual windings in the layer underneath, as would happen in a parallel-wound bobbin. On the face ends of the cheese cone, the yarn makes the transition from one layer to the next, or from one helical line to the other, at a turning point. The turning points at the two face ends constantly change their location within the cheese cone, in order to stabilize the face ends.
Free access to at least one face end of the cross-wound bobbin is needed to allow the yarn to be drawn off from the top, that is, overend. In overend unwinding, the cross-wound bobbin itself remains stationary. The yarn is unwound from the top of the stationary cross-wound bobbin through a yarn eye. The yarn eye is at a distance from the unwinding end of the cross-wound bobbin and is located on the axis of symmetry of the cross-wound bobbin.
From German patent disclosure DE 41 42 886, one such cross-wound bobbin is known in which the pitch traverse differs in the various layers. That is, the inclination of the helical line that the yarn in one layer forms differs quantitatively from the inclination of the helical line in the yarn layer either above or beneath it.
The differing inclination is intended to solve one problem in unwinding the cross-wound bobbin. If the angles of inclination are the same, the yarn can tend to catch at the crossing points, which impairs the unwinding capability. This adhesion increases the unwinding force abruptly, to the point of an overload on the yarn and consequent yarn breakage.
For producing the known cross-wound bobbin, a traversing device is used, which operates at a variable reciprocation speed. The cross-wound bobbin produced is wound up in such a way that the yarn quantity upon unwinding is less if the unwinding point of the yarn on the outside of the cheese cone is moving from the unwinding end to the bottom end, compared to the yarn quantity drawn off if the unwinding point is moving in the opposite direction.
Modern textile machines and especially weaving machines have attained a speed that is limited by the delivery speed of the yarn.